Heat responsive device having separate minimum flame and normal flame responsive elements



2,418,867 HAVING SEPARATE unuuuu IENTS Apz'ii 15, 1947. L. w. BURCH um'rmasrousrva nnvxcs Imus AND nomm. FLAME zmsrousxvm ELE Original FiledSept. 25, 1940 INVENTOR Z ynaon A! 80/66 ATTORNEYS Patented Apr. 15,1947 HEAT RESPONSIVE DEVICE HAVING SEPA- RATE MINIMUM FLAME AND NORMALFLAME RESPONSIVE ELEMENTS Lyndon W. Burch, Pelham, N. Y., assignor toThe Wilcolator Company, Newark, N. J a corporation of Delaware Originalapplication Se No. 358,224. March 15,

13 Claims.

Thi invention relates to. heat responsive apparatus and moreparticularly to a novel apparatus of this character whch operates as theresult of an uneven distribution of heat therein due, for example, toradiation of heat on only a part of the device. The new apparatus issensitive' in operation and may bearranged to provide a positiveactuation in one direction when it is subjected to radiant heat, and toprovide a positive actuation in the opposite direction when the sourceof radiant heat is cut off.

This application is a division of pending application of Lyndon W.Burch, Serial No. 358,224, flied September 25, 1940, for Control systemfor ovens" which became Patent No. 2,361,530 on (Jet. 81, 1944.

For illustrative purposes, the invention will be described in connectionwith a system for indi cating the condition of an oven burner in a gasrangegalthough it will be understood that the invention is not limitedto this use but isapplicable to furnaces and other heat appliances aswell.

Gas ranges as commonly made at the present time are so well insulatedand the oven burner is so completely enclosed that there is little or noevidence that the oven burner is ignited. Accordingly, it sometimeshappens that the burner is left in operation unintentionally after thecooking is completed, with the result that a considerable quantity ofgas is wasted. Also, in gas ranges having means for automaticallylighting the oven burner when the burner is turned on, the operatorusually cannot determine whether or not the automatic lighter hasactually ignited the burner, except by opening the oven door and lookingthrough a vent hole.

It has been proposed heretofore to reduce this hazard by providingadjacent the burner a thermostatic device which, when the burner isextinguished, closes a valve in the supply line to the burner oroperates an indicating device outside the oven. However, the thermostatcannot be of the ordinary type which operates only on temperature changein the oven, because a well insulated oven may remain at a relativelyhigh ptember Z5, 1940, Serial Divided and this application 1944, SerialNo. 526,523

2 circuit. When the burner is ignited, the ceramic element is heated toa temperature at which it becomes an electrical conductor so that thecircuit is closed, but when the burner is extinguished and the elementcools, it no longer conducts current, whereby the circuit is opened.These thermostats are objectionable for various reasons among which aretheir poor response, their tendency to break down under the intense heatfrom the burner, and the fact that they cannot provide a positive motionwithout auxiliary apparatus.

Another form of thermostat previously employed includesa U-shaped memberwhich is inverted overthe flame and provided with a row of holesextending through it near its inner edge, as disclosed in a patent to O..W. Hahn, No. 2,064,909. The holes serve to reduce the heat conducted tothe outer edge of the U-shaped member so that the flame maintains theinner edge at a higher temperature and causes the member to assume anexpanded-position. When the flame is extinguished, the two edges cool tothe same temperature so that the, sides of the member move together.While this form 01' thermostatic element provides a positive movement,it is bulky and relatively expensive to manufacture. Moreover, itsresponse is not sufficientlyrapid for some purposes.

Still another form ot thermostatic device heretofore described by Gordonet al., Patent No. 2,185,436; is formed of a single piece of flat 4strip metal, such as steel, which is bent at its middle so that the twohalves are approximately parallel to each other. The ends of the bentstrip are welded together and the two halves are separated between thebend and the weld by a small air space or. by a layer of asbestos. Thisthermostat is mounted directly over a pilot burner flame so that half ofthe strip is heated while the other is 'shielded, the shielded halfbeing cooled by a current of air. Thermostats of this form are notuniform in character because of the bending and welding operations,which also make for structural failures and imperfections. They arealsorelatively expensive to make because temperature for a long time. afterthe burner is extinguished. In order to provide a quick response toigniting and extinguishing of the burner, it is desirable that thethermostat operof the number of operations involved in theirmanufacture.

The primary feature or the present invention, therefore,. resides in theprovision of a novel thermostat or heat responsive apparatus or devicewhich is simple to make and duplicate uniformly on a mass-productionbasis. According to the disclosure of the above-mentioned appli--cation, the improved thermostat is not of the cients of expansion,

responds to temperature changes in the oven, but is of a type whichresponds only to radiant heat from the burner. A thermostat of this typeis comprised of two metallic elements having substantially equalcoeffithe elements being connected together at their ends but separatedintermediate their ends by a medium which is a poor conductor of heat,the thermostat being mounted in the oven so that one of the metallicelements shields the other from direct radiation from the burner. Apreferred form of the thermostatic apparatus of the present inventioncomprises a tubular metal member having a pair of diametrically opposedslots terminating short of the ends of the member, the slots being sodisposed that they divide a section of the metal tube into two opposedsubstantially parallel elements. Another preferred form of the improvedapparatus of the present invention comprises a pair of such tubularmembers mounted adjacent a burner in the manner described hereinafter.When a tubular thermostatic device of this character, in which theelements have substantially equal coefficients of expansion and areconnected together at their ends but separated intermediate their endsby a medium which is a poor conductor of heat, is mounted in an oven sothat one end is free and one of the elements shields the other fromdirect radiation from the burner, a positive actuation will be eilected.For example, when the oven burner is ignited, the metallic elementsubjected to direct radiation is heated to a higher temperature than theshielded element, and expands relative to the latter so as to move thefree end of the member in one direction. On the other hand, when theoven burner is extinguished, the two elements quickly assume the sametemperature, that is, the temperature in the oven, and the free end ofthe member moves back to its original position.

The pending application referred to above discloses an indicating systemfor positively indicating to the operator when an oven burner isactually lighted, so as to afford an indication equivalent to thatusually provided on electric ranges by the pilot light. This systemmakes use of a thermostat or heat responsive apparatus of the type ofthat of the present invention mounted in the oven adjacent the ovenburner. so that it receives direct radiation from the burner flame. Themovable and of the heat responsive member is connected toa contact whichis movable by the member relative to a fixed contact. These two contactscomprise a switch which may be included in the circuit of an indicatingdevice, such as a lamp bulb, mounted outside the oven where it isvisible to the operator. Preferably, the system is used with a range ofthe type in which the oven burner is throttled to provide a lowmaintaining flame when the desired temperature is reached, and thecontacts are arranged so that they are normally open to de-energize theindicator when the burner is not operating. Accordingly, when the burneris ignited, the contacts are closed by the radiant heat thermostat toenergize the indicator, and 'the operator will therefore know that theburner is operating as called for by the position of the adjustmenthandle of the usual thermostatic valve. Should the burner beaccidentally extinguished for any reason, the radiant heat thermostatwill quickly open the contacts and tie-energize the indicator, so thatthe operator will be warned to turn the adjustment handle to its "of!"position or ordinary type which relight the burner. If the burner shouldfail to ignite when the adjustment handle is turned to one of its on"positions, the contacts will remain open and the indicator de-energized,thereby warning the operator. The radiant heat thermostat operatesindependently of the oven temperature and causes the indicator to remainenergized even when the oven burner is operating with a minimummaintaining flame.

The pending application also discloses an indicating system in which theapparatus of the present invention may also be employed for indicatingwhen the oven burner has heated the oven to the temperature for whichthe adjustment handle of the usual thermostatic regulating valve is set.In this system a radiant heat responsive member of the type of that ofthe present invention is mounted in the oven adjacent the oven burner,but is so positioned with respect to the burner that it'operates onlywhen the burner provides a substantial amount of radiant heat; that is,the radiant heat responsive member returns to its initial positionwhenever the oven burner is operating with a minimum temperaturemaintenance or by-pass flame, or whenever the burner is extinguished.The radiant heat thermostat also preferably operates a pair of contactsin circuit with an indicator, so that when the oven burner is turned onand ignited, the indicator is energized, but when the desiredtemperature is obtained and the thermostatic valve throttles the burner,the radiant heat therefrom is not sufiicient to hold the radiant heatthermostat in its actuated position, whereby the indicator isde-energized,

If desired, the indicating system according to said application mayinclude two radiant heat thermostats, one operating on both minimummaintenance and normal burner flame and the other on only a normalflame, and each thermostat may operate an indicating device so that theoperator is informed whether the burner is ignited or extinguished andis also informed when the desired temperature is attained.

Other features, objects and advantages of the present invention will beexplained more in detail in connection with the accompanying drawings.in which:

Fig. 1 is a broken view partly in horizontal section, showing one formof the new heat responsive apparatus or thermostatic device applied tothe oven of a gas range.

Fig. 2 is an enlarged vertical sectional view of the apparatus taken onthe line 2-2 of Fig. i.

The new heat responsive apparatus or thermostatic device as shown, isapplied to a gas range including an oven in having a main gas burner iimounted therein, the burner being provided with suitable jets Ila. Gasfor the oven burner ii may be supplied in the usual way through aconventional regulator (not shown) which may be connected to athermostat (not shown) responsive to temperature changes in the oven. Insystems of this type, the oven thermostat actuates the regulating valveto supply more or less gas in accordance with variations in the oventemperature, to counteract any temperature variation.

Mounted in the oven i0 adjacent the main burner Ii are two similar heatresponsive members or thermostats 3B and 31 which are responsive only todirect radiation from the main burner i i. The thermostats 36 and 31 maytake any desired form but preferably they comprise tubular members asand 38a, respectively, made of metal,

and each having a pair of diametrically opposed slots as and "a,respectively. extending lengthwise oi the tube but terminating short 01the ends of the tube, the slots being so disposed that they divide asection of each tube into two opposed elements one of which faces theburner and the other of which is shielded by the ilrst element. At theirinner ends. the tubular members are mounted in a hollow metal casing 40so that the tubes communicate with the interior oi the casing. Fittedclosely in the free ends oi the tubes are metal collars 4i and Ma,respectively. supporting rods 42 and 42a. respectively, which extendinwardly through the tubes in spaced relation thereto and proiect intothe casing 40. The free ends of the rods 42 and 42a coact with fixedcontacts 48 and 43a, respectively, mounted on suitable insulatingsupports 44, the fixed contacts and their corresponding rods formingseparate control means ior a purpose to be described presently. 1

The side of the casing 40 opposite the tubular members 38 and 38a isprovided with a hollow boss 48 having a generally spherical portion 41intermediate its ends. A metal bracket 48 has a circular opening thereinfor receiving one end of the spherical portion 41 and is connected bybolts 48 to a plate 50 having a similar opening for receiving the otherend of the spherical portion. Thus. the spherical portion 41 and thecoacting bracket 48 and plate 50 provide a universal mounting for thehousing so that the latter may be adjusted to position the tubularmembers 48 and "a relative to the Jets of the oven burner. The bracket48 is preferably connected to the adiacent side wall oi the oven 10 sothat it is grounded, as shown as 5|. Threaded on the outer end of thehollow boss 48 is a compression fitting ll engaging an enlargement B4 onthe end of ametal tube 58 which extends through the adjacent wall of theoven. The fitting 53 is screwed tightly on the boss so as to clamp theenlargement 54 against the outer end of the boss.

The fixed contact 43 has a wire 51 connected thereto which leads fromthe interior of the easing through the boss 46 and tube ill to the outside of the oven where it is connected to one terminal oi a suitableindicating device such as an incandescent lamp. Similarly, the nxcdcontact 43a has a wire 60 connected thereto, leading through the boss 48and tube 5! to one terminal of a second suitable indicating device, suchas an incandescent lamp. The other terminals of the indicating devicesor incandescent lamps may be connected to a source of electrical powerwhich would be grounded to the stove or connected to the ground lead II,to form a complete circuit.

In operation, the rods 42 and 42a disengage their corresponding contactswhen the oven burner I I is extinguished, thus de-energizing theindicating devices. When gas is turned on in the oven and the burner iiignites. as for example, by a suitable pilot, the resulting radiant heatfrom the burner flame strikes the adjacent thermostat 38 and heats theadjacent side oi this thermostat to a higher temperature than the remoteside, with the result that the adjacent side expands relative to theremote side and causes the free end of the thermostat to move away fromthe burner and tilt the rod 42 in a counter-clockwise direction, therebycausing the inner end of the rod to engage its fixed contact 43. Acircuit is then established through the indicating device. such as alamp, from the round or other connection II, through bracket 48, casing40, tube II,

6 collar 4i. rod 42, contact 43, wire 87, and back to the indicatingdevice or lamp which is connected through a source oi electric power tothe range or to connection H. The external indicating dc vice is thusenergized and informs the operator that the main burner is ignited.

Similarly, the thermostat 31 is subjected on one side to directradiation from the main burner ll, although the radiant heat on thisthermostat is not as intense as it is on the thermostat 38, due to thefact that the thermostat 31 is located at a greater distance from themain burner ii and is partly shielded therefrom by the thermostat I6.However, when the main burner is operated with a normal name, as when itis heating the oven up to the desired temperature or which the regulatoris set. the radiant heat on the side of the thermostat 3'! adjacent theburner Ii is sufficient to cause this side to expand relative to theopposite side, so that the free end of the thermostat 81 moves away fromthe burner and causes its rod 42a. to engage the corresponding fixedcontact 48a. A circuit is thus established irom the ground connection llthrough bracket 48, casing 40. tube 88a. collar 4la, rod 420. fixedcontact 43a. wire 60. the indicating device. and back through a sourceof electrical energy to a ground connection to the range, or directly tothe wire of the ground 8|.

when the temperature-in the oven has reached that for which the ovenregulator was set, the gas supply isthrottled to give a minimum ormaintaining flame on the burner H. The radiant heat from this minimumilame is sui'ilcient to maintain the required temperature differentialbetween the opposed sides of the thermostat 38 to cause the latter tohold its rod 42 in engagement with contact 43. and thus energize theindicating device. However. radiant heat from the minimum llama is notsufiicient to maintain the required temperature differential in thethermostat 81. and the opposed sides or the latter tend to approach auniform temperature so that the tube 380 rcturns toward itsnormaliposition and discnaagcs its rod 42a. from the fixed contact 48a.As a result. the circuit through the indicator or lamp is broken and thelatter dc-encrgized. thereby indicating to the operator that the desiredtempera-- ture has been reached in the oven.

Ii ior any reason the oven burner H should be extinguished, the opposedsides oi the thermostat 38 will quickly assume a uniform tempcrature andcause the free end of the thermostat to move toward the burner anddisengage the rod 42 from its fixed contact 43. The circuit from thisthermostat is then broken and the indicator or lamp deencrgized toindicate to the operator that the main burner is not operating.

The new heat responsive apparatus is of simple construction and isreadily installed in a range. The operator may determine by a glance atthe indicators operated through control means by the thermostats I4 and31, whether the oven is actually operating, as called for by the ovenregulator, and whether the oven has been heated to the temperature forwhich the regulator is set. In the event that the burner H tails tooperate when the gas is turned on, the operator is immediately andpositively informed at the dangerous condition by the absence ofillumination from the lamp or other indicator connected to thethermostat 38. I! the current for cncraizihg the indicators should beinterrupted, they to function, the operator is warned that either theburner is not ignited or that the indicating system has not responded.Since the switches 42, 43 and 42a, 43a, for controlling the indicators,are housed by the casing 40 and the slotted tubes, they are protectedagainst damage by food inserted in the oven, grease, etc. Also, byreason of the universal mounting for the casing 40, the latter may bereadily adjusted to place the tubes 38 and 38a in their proper positionsrelative to the adjacent burner jets Ila, and when the adjustment iscompleted, the bolts 49 may be tightened to hold the parts securely inposition. It will be apparent to those skilled in the art that theslotted members may be made inexpensively and uniformly by a simple slotcutting operation on standard tube stock or on equivalent stock ofsimilar shape.

With the use of the improved heat responsive apparatus, it is unlikelythat the operator will accidentally leave the burner turned on after thefood is removed from the oven, because the lamp or other indicatorassociated with the thermostat 36 remains illuminated or active as longas the burner is operating, even with a minimum flame. While in theillustrated form of my invention the thermostats of heat responsivemembers 36 and 31 energize the indicators only when they are actuated byradiant heat, it will be understood that the parts may be arranged so asto energize the indicators whenever the radiant heat thermostats returnto their normal positions and to de-energize the indicators when theirrespective thermostats are actuated by the radiant heat. With the latterarrangement, the indicators would be de-ener gized automatically whenthe oven regulator is provided with a switch in the indicator circuits,which is opened when the regulator is turned to its off position.

I claim:

1. A heat responsive apparatus comprising an elongated tubular-shapedmetal member having a section intermediate its ends slotted lengthwiseof the member to form a pair of opposed substantially parallel segments,one end of said member being rigidly mounted and the other end beingfree and deflectable from its normal position with respect to the otherend of the member by the unequal heating and expansion of said segmentswhen said member is disposed with one or said segments shielding theother from direct radiation from a source of heat.

2. A thermal responsive device comprising a metal rod having alongitudinal slot therethrough forming two parallel members, means i ormounting the rod adjacent a source of radiant heat with one of saidmembers shielding the other from the source of heat, whereby flexurewill result from a difference in temperature between the two saidmembers, said slot extending through a portion only of the rod lengthand leaving unslotted a substantial portion thereof.

to said burner so that it is responsive to a mini- 4. In a heatresponsive apparatus for a burner,

two elongated metal flexing heat responsive members each having asubstantial section intermediate its ends slotted through to provide twosubstantially parallel segments opposite each other, means for mountingone end of each of said members near the burner with one of the segmentsof each member shielding the other segment thereof from direct heatradiation from the burner, whereby flexure of each member will resultfrom a diiference in temperature between the two segments thereof, oneof said members being mounted with respect to saidburner so that it isresponsive to a minimum and to a normal flame thereon, the second ofsaid members being mounted a greater distance from said burner than theother member and partly shielded from the burner flame by said othermember so that it is responsive to a normal flame but not responsive toa minimum flame on the burner, and means for utilizing the flexure ofeach of said members to operate a control device.

5. In a heat responsive apparatus, an elongated tube having a sectionintermediate its ends slotted lengthwise of the tube to form a pair ofopposed substantially parallel segments, one end of said tube beingrigidly mounted in a casing and opening thereinto while the other end oithe tube is free and deflectable irom its normal position with respectto the fixed end of the tube by the unequal heating and expansion ofsaid segments when said tube is disposed with one of said segmentsshielding the other from radiation from a source of heat, and controlmeans in the casing operable by the deflection or the free end oi thetube.

6. In a heat responsive apparatus, an elon gated metal tube having asection intermediate its ends slotted lengthwise of the tube to form apair of opposed substantially parallel elongated segments, one end ofsaid tube being rigidly mounted in a housing and opening thereinto whilethe other end of the tube is free and deflectable from its normalposition with respect to the rigidly mounted end of the tube by theunequal heating and expansion of said segments when said tube isdisposed with one of said segments shielding the other from radiationfrom a source of heat, a movable contact in the housing connectedelectrically to the free end of the tube and operable by deflectionthereof, and a flxed contact in the housing coacting with the movablecontact and insulated from the housing.

'7. In a heat responsive apparatus, an elongated metal tube having asection intermediate its ends slotted lengthwise of the tube to form apair of opposed substantially parallel elongated sag ments, one end ofsaid tube being rigidly mounted in a casing and opening thereinto whilethe other end of the tube projects from the casing and is free anddeflectable from its normal position with respect to the fixed end ofthe tube by the unequal heating and expansion of said segments when saidtube is disposed with one of said segments shielding the other fromradiation from a source of heat, a metal rod connected tel theprojecting free end of the tube and extending through the tube into thecasing in spaced relation to the tube wall, a movable contact in thecasing mounted on the free end of the rod and operable by the deflectionof the tube and rod, and a fixed contact in the casing coacting with themovable contact and insulated from the cas- 8. A heat responsiveapparatus comprising an e gated metal tube having a. longitudinal slotthe ,ethrough forming two parallel members, means for mounting the tubeby one end only with the other end, free adjacent a source of radiantheat with one of said members shielding the other from the source ofheat, whereby flexure will result from a difierence in temperaturebetween the two said members, said slot extending through a portion onlyof the length of the tube and leaving unslotted the end portionsthereof, and'a control device operatively connected to the free end ofthe .tube and responsive to the fiexure thereof.

9. A heat responsive device comprising an elongated thermo-responsivemember including a pair of elongated substantially parallelthermoexpansible elements of equal coefflcients of expansion connectedtogether at their respective ends and separated from each other by a,slot through a substantial portion of their lengths, means for rigidlymounting said member by one end only with th other end free adjacent asource of radiant heat with'one of said elements shielding the otherfrom the source of radiant heat, whereby flexure of said member willresult from a difference in temperature between the two said elements, arod connected in fixed position between said elements at the free end ofsaid member and extending between the elements with a clearance, and acontrol device operated by the rod in response to the flexure of themember.

10. A thermal responsive device comprising a metal rod of round crosssection having a longitudinal slot therethrough forming two parallelmembers, means for mounting the rod adjacent a source of radiant heatwith one of said members shielding the other from the source of heat,whereby flexure will result from a diil'erence in temperature betweenthe two said members.

11. A heat responsive device comprising an elongated metal member ofround cross section having a longitudinal slot therethrough intermediateits ends, said slot forming two substantially parallel segments, andmeans for rigidly mounting said member adjacent a source or radiantheatby one end only while the other end is free, said member beingmounted with one of said segments exposed to radiation from said sourceand shielding the other segment therefrom, whereby flexure of the memberwill result from a difference in temperature between the two segments.

12. A heat responsive apparatus comprising an elongated metal tubehaving a longitudinal slot therethrough forming two parallel members,means for mounting the tube with one end free adjacent a source ofradiant heat with one of said members shielding the other from thesource of heat, whereby flexure of the tube will result from adifference in temperature between the two said members, said slotextending through a portion only of the length of the tube and leavingunslotted the end portions thereof, a control device, and means withinsaid tube for transmitting movement caused by the deflection of the tubeto the control device.

13. In a heat responsive apparatus, an elongated metal tube having asection intermediate its ends slotted lengthwise of the tube to form apair of opposed substantially parallel elongated segments, one end ofsaid tube being rigidly mounted in a casing and opening thereinto whilethe other end of the tube is free and deflectable from its normalposition with respect to the fixed end of the tube by the unequalheating and expansion of said segments when said tube is disposed withone of said segments shielding the other from radiation from a source ofheat, a rod of substantially smaller cross-section than that of saidtube fixed to and rigidly mounted in the free end of the tube andextending through the tube into the casing, and a control means in thecasing operable by the rod in response to a deflection of the free endof the tube.

LYNDON W. BURCH.

REIERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

